A one-time programmable (OTP) memory may be used to provide additional security for the data stored in the OTP memory. Once a bit in an OTP memory is programmed, for example, from a binary zero to a binary one, then that particular bit typically cannot be programmed again.
Data stored in the OTP memory may also be protected with error codes. For example, a cylindrical redundancy checking (CRC) code may be used for error detection and a Hamming code may be used for error correction. Thus, the data, possibly several Hamming codes and one CRC code are then all stored in the OTP memory. Each Hamming code is a function of a portion of the data stored in the OTP memory. The CRC code is a function of the data and the Hamming codes stored in the OTP memory.
The conventional OTP memory may have one or more of the following disadvantages. For example, information stored in the OTP memory is inflexible since the data cannot be changed. A change in one bit that is covered by a Hamming code is corrected by the Hamming code. Thus, the change in the one bit has no effect. In addition, a change in one bit that is covered by the CRC code changes the CRC code, which may be interpreted as evidence of tampering by the OTP memory. Thus, if the data is protected by an error code, then the data cannot be modified.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of ordinary skill in the art through comparison of such systems with aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.